Know the Lingo: Hurricanes and Typhoons

Tropical Terminology

Invest

When a tropical weather center (like the National Hurricane Center or the Joint Typhoon Warning Center) are interested in collecting special datasets for an area of disturbed weather, they call it an "invest," because they are investigating the system for potential development. The designation of "invest" doesn't correspond to any likelihood of development, but it does mean there's an area of disturbed weather, and the organizations are looking into it.

Tropical Cyclone

A generic term for warm-core weather systems that occur in the tropics, like tropical storms, hurricanes, and typhoons.

Tropical Depression

A tropical cyclone in which the maximum sustained surface wind speed is less than 39 mph (34 knot).

Tropical Storm

Hurricane

A tropical cyclone in which the maximum sustained surface wind is 74 mph (64 knots) or more.

Major Hurricane

A hurricane with winds greater than 110 mph (category 3 or higher on the Saffir Simpson hurricane wind scale).

Typhoon

A tropical cyclone that forms in the Pacific Ocean between 180° and 100°E. Typhoons are similar to hurricanes, and require winds 74 mph (64 knots) or greater.

Super Typhoon

A tropical cyclone in the Northwestern Pacific with winds of 114 mph (130 kt) or greater (category 4 or greater on the Saffir Simpson hurricane wind scale) is designated a "Super Typhoon."

Storm Surge

An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide. Storm surge can reach heights well over 20 feet and can span hundreds of miles of coastline.

Watches, Warnings, and Advisories

Hurricane Warning

An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.

Hurricane Watch

An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.

Tropical Storm Warning

An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are expected somewhere within the specified area within 36 hours.

Tropical Storm Watch

An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are possible within the specified area within 48 hours.

Short Term Watches and Warnings

These watches/warnings provide detailed information about specific hurricane threats, such as flash floods and tornadoes.

Saffir Simpson Hurricane Wind Scale

Category

Wind Speed

Expected Damage

1

74 - 95 mph
64 - 82 knots

Very dangerous winds will produce some damage
- Minor damage to exterior of homes
- Toppled tree branches, uprooting of smaller trees
- Extensive damage to power lines, power outages

2

96 - 110 mph
83 - 95 knots

Extremely dangerous winds will cause extensive damage
- Major damage to exterior of homes
- Uprooting of small trees and many roads blocked
- Guaranteed power outages for long periods of time—days to weeks

3

111 - 129 mph
96 - 113 knots

Devastating damage will occur
- Extensive damage to exterior of homes
- Many trees uprooted and many roads blocked
- Extremely limited availability of water and electricity

4

130 - 156 mph
114 - 135 knots

Catastrophic damage will occur
- Loss of roof structure and/or some exterior walls
- Most trees uprooted and most power lines down
- Isolated residential due to debris pile up
- Power outages lasting for weeks to months

5

Greater than 156 mph
Greater than 135 knots

Catastrophic damage will occur
- A high percentage of homes will be destroyed
- Fallen trees and power lines isolate residential areas
- Power outages lasting for weeks to months
- Most areas will be uninhabitable

Some content from: Ready.gov

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